Chart C, Inflatable Restraint Indicator Comes On Steady: Description

When ignition switch is first turned on, system voltage is applied through METER fuse to SIR INDICATOR HIGH B9 and to INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW A1. SIR fuse also applies system voltage to IGNITION 1 inputs A3 and B3. DERM responds by flashing INFLATABLE RESTRAINT indicator light 7 times.

Purpose of shorting bar is to turn INFLATABLE RESTRAINT indicator light on should DERM become disconnected.

When engine is being cranked, system voltage is applied to DERM at CRANK input. DERM grounds lamp circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator light during cranking.

After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator light 7 times.

1. An open SIR fuse would result in a loss of IGNITION 1 voltage at DERM. DERM will respond by grounding lamp circuit (SIR INDICATOR LOW) whenever ignition switch is on.
2. If DERM and SIR harness connector are disconnected, shorting bar between terminals No. A1 and B1 of harness connector will ground lamp circuit.
3. Checks for a short to ground in IGNITION 1 circuits or DERM.
4. Checks if there is a short to ground on low side of lamp circuit external of DERM. SIR load tool prevents shorting bar in DERM connector from grounding lamp circuit.
5. Checks if short to ground is in DERM on IGNITION 1 circuits.
6. Checks for IGNITION 1 voltage at DERM. If IGNITION 1 circuits are open, DERM will ground lamp circuit whenever ignition switch is on (if SIR INDICATOR HIGH circuit is good).
7. Checks for a short to system voltage in CRANK circuit.

Fig 1: Chart C, Inflatable Restraint Indicator Comes On Steady

Courtesy of GENERAL MOTORS CORP.